I think that’s a good point. I have no proof for this, but in my experience, the negativity bias is somewhat more powerful.
So yes, if the bad thing happens first and the good thing later in the day, that makes the bad feel less pronounced, as I’ll try to draw from the good first in my memory, but if I assess the day two days later, I might emphasize the bad again, even though it’s not as strong of a bad memory as if the bad had come last.
Feels like the availability heuristic is a countering force, but not one that is likely to overpower negativity bias altogether — exceptions prove the rule! If something exceptionally great happens late in the day, that sure can turn things around every now and then!